Method of treating soybean oil



Dec. 18, 1962 N. H. WITTE ETAI. 3,

METHOD OF TREATING SOYBEAN OIL Filed Sept. 17, 1959 CRUDE DEGUMMEDSOYBEAN OIL DRYING METHANOL PHASE CONTAINING XANTHOPHYLL OIL PHASE FLASHEVAPORATOR SEPARATION STEAM STRlPPlNG QI A F O Q UNDER VACUUM METHANOLAND WATER XANTHOPHYLL VAPORS CONCENTRATE COOLING STEAM STRIPPING UNDERVACUUM REFINED WATER VAPOR SOYBEAN H- CONTAINING LAST TRACES I OFMETHANOL INVEN 0R5 I W gm @044 'womg By 7W;

ATTORNEYS.

hired States Patent @Efice asserts Patented Dec. 18, 1952 sesame METHQDF TREATING SUYBEAN Norman H. Witte and Entire ipos, Decatur, ind,assignors to Central Soya Company, The, Decatur, End, a corporation ofIndiana Filed Sept. 17, 1959, Ser. No. 840,718 4 (Ilainis. (l. 260d28.5}

This invention relates to a method of treating soybean oil. Morespecifically, the method of this invention is adapted to improvethequality of the soybean oil while at the same time recovering axanthophyll concentrate as a by-product. The xanthophyll concentratethus obtained can then be mixed with animal feeds, particularly feedmaterials forpoultry, for the purpose of providing a yellow pigmentationagent in the feeds, or the concentrate can be used as a yellow coloringagent for foods.

One of the objects of this invention is to provide an improvedmethod ofrefining soybean oil and other vegetable oils. A further importantobject is to provide a method of recovering and concentrating thexanthophyll which is present in relatively minute or trace amounts incrude soybean oil. Another more comprehensive objective is to provide amethod of improving the quality of soybean oil and at the same timerecovering the xanthophyll in usable form. Further objects andadvantages will appear as the specification proceeds.

The method of this invention in one of its embodiments is illustrated inthe attached fiow sheet. it is to be understood, however, that themethod can involve variations from the processing steps illustrated inthe flow sheet without departing from the essential procedures andconditions of the present invention, as described more fullyhereinafter, and in the attached claims.

In practicing the method of this invention, it is preferred to startwith a degurnmed soybean oil. The lecithin material which is normallypresent in substantial amounts in crude soybean oil is co-extracted withthe xauthophyll which reduces the concentration of the xenthophyllextract. Consequently, it is preferred to remove most of the lecithinmaterial from the soybean oil before it is subjected to the extractionprocedure of the present invention. This can be accomplished by theconventional degumming procedure wherein the soybean oil is treated withwater (or with live steam) to hydrate the lecithin-phosphatidicmaterial, and the hydrated material is then separated by a suitableprocedure such as centrifuging. Other methods can also be employed toreduce the lecithin content of the crude oils. When it is desired torecover the xanthophyll as a lay-product, it is important that thedegumming proce tre carried out in such a Way that removal ordestruction of the xanthophyll is largely avoided. Xanthophyll issensitive to acidic mediums, and to prolonged heating at temperatures ofl60-l70" P. or above.

Crude soybean oil may contain from 2 to 6 percent of phcsphtidic-lecithin material, which comprises most of the non-triglyceridematerial in the oil. Degurnmecl soybean oilsuitable for use inpracticing the present invention will usually contain a total of lessthan 2 crcent of non-triglyceride material and preferably less th u lper-- cent, these percentages being on a Weight basis. On the otherhand, the degum'ning treatment does not remove all of thenon-triglyceride material, leaving the xan ophyll and othernon-triglyceride com ounds for suesequent removal. This is done in thealkali-refining, bleaching and deodorizing steps of present soybean oilrefining processes. According to the method of the present invention, arefined soybean oil of acceptable flavor and color can be obtainedwithout the need for a conventional alkali-refining step and with lesssevere bleachiug conditions.

The degummed soybean oil suitable for practicing the present inventionwill usually contain at least 98 percent by weight triglyceride oil withthe remainder comprising non-triglyceride components including thexanthophyll.

The crude degummed soybean oil is very likely to contain more water thancan be tolerated in the process of this invention. it will therefore beimportant to con trol the moisture content of the degummed oil, and whenthe percentage of water therein is excessive, the oil should besubjected to a drying step. It is preferable to dry the oil to asubstantially anhydrous condition. In practice the moisture content ofthe oil can be kept Well below 0.3% by wei ht.

in the next and most basic step of the present process, the degummedsoybean oil containing the xanthophyll is subjected to extraction withmethanol under substantially anhydrous conditions. in this extraction,the xanthophyll collects in the methanol phase. Consequently, in thesubsequent steps of the process, as will be ex plain-ed in greaterdetail, the xanthophyll-containing methanol phase is separated from theoil phase, and the small proportion of meth nol which is dissolved inthe oil phase is removed therefrom to obtain the treated soybean oil.

As already indicated, the methanol extraction is preferably carried outunder substantially anhydrous conditions. it is therefore desirable tocontrol the moisture content not only of the soybean oil but also of themethanol. Preferably, the extracting solvent is practically anhydrousmethanol. During the extraction, no part of the extraction system shouldcontain in excess of 2 percent water, and preferably not in excess of 1percent water by weight. The methanol phase will normally contain morewater than the oil phase, the water being preferentially soluble in themethanol. Optimal results are obtained when the moisture content in themethanol phase is controlled to about .3 to .5 percent or less, and theoil phase has an even lower moisture content.

Where the degumined oil contains excessive moisture, as will normally tothe case, it can be dried to a moisture content of as low as .1 percentby preheating it to a temperature of around F, spraying the heated oilinto the top of a column main ained under reduced pressure, and therebyflashing oft the Water. Methanol of suitably low water content can beobtained commercially. Commercial grades of methanol may contain around.3 percent water by weight. Since it will be desirable to recover andre-us the methanol, it will be desirable to provide distillingfacilities, whereby the methanol after separation from the xanthophyllmaterial and from the oil can be reduced to very low moisture content.

The use of methanol in the extraction step is quite critical, since noother solvent has been found which will give equivalent results in caseswhere the maximum concentration of xanthophyll is desired in theextract. However, ethanol and other low molecular Weight alcohols can beused when the primary object of the process is to produce a superiorrefined oil and lower xanthophyll concentrations in the extract can betolerated. The extraction can be carried out in any suitable equipment,such as contact columns, centrifugal contactors, and with lesseradvantage in a plurality of mixers and settlers. Preferably the methanoland oil are contacted countercurrently, and the extracting equipment isdesigned to provide a plurality of stages. When a multiple stage,countercurrent extraction procedure is followed and the oil and methanolphases are substantially free of water, the other process conditions arerelatively noncritical. For example, solvent ratios of one to two partsby weight of alcohol per part of oil are satisfactory, although othersolvent ratios can also be employed. The extraction temperatures mayrange from 40 F. or lower to 140 F. Good results are obtained attemperatures of around 125 to 130 F. At temperatures above 140 F. themutual solubility of the oil and alcohol tends to become excessive, andof course the system must be operated below the boiling of methanol(about 156 F. at atmospheric pressure) unless pressure conditions areemployed. At lower temperatures, the viscosity of the oil may increaseto a point where good contact efliciency cannot be obtained.

According to the method of the present invention, the extraction can becarried out without chemical modification of the oil or xanthophyll.There is no need to employ auxiliary reagents. The presence of acidicmaterials or reagents which would effect the stability of thexanthophyll should be particularly avoided.

Although soybean oil contains a relatively minute amount of xanthophyllof the approximate order of 65 micrograms of xanthophyll per gram ofoil, the method of this invention provides a means for obtaining thexanthophyll in a sufficiently concentrated form to permit it to be usedas a pigmentation agent in poultry feeds or as a food color.Consequently, where the preparation of a xanthophyll concentrate isdesired as a by-product of the oil refining procedure, thexanthophyll-containing methanol phase is separated from the purifiedoil, and subjected to further processing for the purpose of recoveringthe methanol while at the same time preparing the Xanthophyllconcentrate.

The methanol phase will contain a small percentage of triglyceride oiltogether with most of the xanthophyll and other non-triglyceridematerials. If desired, part of the triglyceride oil can be removed fromthe methanol phase by reducing the temperature thereof to from 40 to 7015., thereby forming a separate oil phase which can be removed bycentrifuging, or by a settling and decanting procedure. Such a chillingprocedure is not necessary, however, and in accordance with thepreferred embodiment of the present invention, the oil in the methanolphase is carried through into the xanthophyll concentrate, therebyobtaining a product which can readily be mixed with poultry feeds. Whensome of the oil is removed from the methanol phase, there will be afurther concentration of the xanthophyll in the final product, but evenwhere the methanol phase contains from 1 to 2 percent of the totaltriglyceride oil of the starting material, xanthophyll concentratescontaining at least 500 units of xanthcphyll per gram of concentrate canbe obtained. (1 unit of Xanthophyll is equal to 1 microgram.)

In the processing of the methanol phase the methanol can be separatedfrom the xanthophyll in oil by a suitable evaporation procedure, such asa flash evaporator separation. The resulting oil solution of xanthophyll(the tranthophyll concentrate) can then be subjected to steam stripping,preferably under vacuum to avoid destruction of the xanthophyll, for thepurpose of removing the last traces of the methanol. The removal of thewater and methanol vapors will yield a product comprising a xanthophyllconcentrate which is non-toxic and in which the xanthophyll issufiiciently stable to permit the product to be stored for long periodof time. As indicated above, this product is well adapted for mixingwith poultry feeds. This product will consist of a soybean oil fraction(triglycerides, fatty acids, phosphatides, sterols, tocopherols, colorbodies, etc.) containing at least 500 units of xanthophyll per gram ofconcentrate and will be substantially free of methanol.

Turning to the discussion of the procedure for refining the soybean oil,the oil phase after removing the methanol phase will contain a smallpercentage of dissolved methanol. For example, the oil phase may containfrom 5 to 8 percent by weight of methanol. The methanol can then beremoved by any suitable procedure, such as steam stripping under vacuum.The methanol and water vapors are removed, and the refined oil isthereafter preferably cooled before being stored or shipped. It isimportant agent to obtain the same deg that the methanol be completelyremoved from the oil to avoid any toxicity problem due to residualmethanol.

The extraction of the oil with the methanol is preferably continuedthrough three or more countercurrent extraction stages. By following theprocedure described above and using a sufficient number of stages, ithas been found possible to not only remove substantially all of thexanthophyll pigments but also to remove the other nontriglyceridecomponents. For example, a degummed soybean o-il containing from .3 to.5 percent by weight of non-triglycerides on an absolute loss basis atthe start of the extraction treatment can have the percentage ofnontriglycerides in the oil reduced to less than .1 percent by therefining procedure of this invention. In other words, the beany flavorin soybean oil and many of the pigments in the oil, which are normallyremoved in the bleaching and deodorizing st ps of present processes, canbe removed from the oil by the extraction procedure described herein.The process of this invention therefore results in an oil which canqualify as a refined soybean oil, and which can be sold for consumptionfor some food uses without further processing. In using the process forproducing a high grade refined oil, it is therefore preferred that theextraction be continued until the oil contains less than 0.1 percent ofnon-triglyceride material as determined by the A.O.C.S. absolute lossdetermination and break-free by the Gardner Heat-Break Test.

For certain uses, it may be desirable to subject the oil to a mildbleaching treatment. Even where a further b eaching treatment isdesired, the methanol extraction method of this invention has a definiteadvantage over conventional refining procedures, such as the widely usedalkali refining method. It has been discovered that the methanol refinedoil requin less of the bleaching reree of color improvement. Thisprovides considerable saving in the cost of the bleaching material, suchas the activated fullers earths of which the A.O.C.S. ActivatedBleaching Earths is one. By using as little as 2 percent of an A.O.C.S.Bleaching Earth, a final product can be obtained which will pass theA.O.C.S. Gardner-Acid-l'ieat-Break Test. This is the most stringent ofthe Gardner tests, and indicates that the undesirable materials havebeen entirely removed.

The preferred method of practicing this invention is further illustratedby the following example.

Example Degummed soybean oil which is substantially free oflecithin-phosphatidic material is preheated to 180 F. and sprayed intothe top of an evacuated Column of flash off the water. In this dryingoperation, the Water content; of the oil is reduced to approximately0.03% by weight The dried cil contains about 0.5% by weight on anabsolute loss basis of non-triglyceride material in addition to thesmall amount of water therein. The non-triglyceride material includesxanthophyll pigments in the amount of approximately 60 micrograms pergram of oil. This oil is then subjected to a multiple stagecountercurrent extraction with methanol containing about .3 percentwater by volume. The extraction is carried out at a temperature of aboutto l. and at a solventzoil ratio of about 1:1. The extraction is carriedout in a contactor column of standard design, the extraction beingcontinued until the oil phase contains less than .1 percent ofnon-triglyceride organic material.

The methanol phase which contains approximately 1 percent by volumetriglyceride oil in addition to the extracted non-triglyceride materialis separated from the oil phase, and. subjected to further processing toprepare a xanthophyll concentrate. The methanol is stripped from thetriglyceri is removed by steam strippi de and non-triglyceride materialsunder con-- ditions which prevent destruction of tl e xanthophyil.v ovedby a flash evaporator Sepng under vacuum- T he results ing xanthophyllconcentrate contains about 2,600 micrograms of xanthophyll per gram ofoil (an increase in concentration of about 50 times over that of theoriginal oil). An analysis of the concentrate shows that it containsabout 58 percent triglyceride, 25 percent free fatty acids, 13 percentacetone insoluble, and 4 percent of sterols, unsaponifiables, etc.

This concentrate can then be mixed with poultry feed rations which aredeficient in xanthophyll pigments.

The small percentage (about 6 percent by Weight) of the methanol in theoil phase is removed by steam stripping the oil under vacuum. The oil isthen cooled to provide a refined soybean oil product which contains lessthan 0.1 percent non-triglyceride material as indicated by the absoluteloss determination and the ability of the oil to pass theGardner-Heat-Break Test, which is a modification of theGardner-Acid-Heat-Break Test wherein no acid is used. Part of this oilwas then treated with 2 percent of an A.O.C.S. Bleaching Earth. The oilsubjected to the further bleaching treatment passed the A.O.C.S.Gardner-Acid-Heat Break Test.

On the basis of the foregoing example and description, it is believedthat the attached flow sheet Will be largely self-explanatory. The boxescentered on the vertical lines describe the materials being processed,while the boxes to the right of these lines describe the processingsteps. The boxes on the horizontal line extending to the left describethe materials being removed at various points in the process. Thestarting material is the crude degummed soybean oil as indicated in thebox at the top of the sheet, and the final products are the refinedsoybean oil and the xanthophyll by-product as indicated in the boxes atthe bottom of the flow sheet.

While the refining procedure of this invention is particularly adaptedfor the treatment of soybean oil, it is contemplated that it can also beadvantageously applied to other triglyceride vegetable oils. In treatingother vegetable oils, it may be desirable to utilize the methanolextraction procedure described herein to improve the quality of the oilby removing non-triglyceride material therefrom even though it is notdesirable or feasible to prepare a. xanthophyll concentrate as aby-product.

While in the foregoing specification many procedural details have beenset forth for purpose of illustration, it Will be apparent to thoseskilled in the art that certain of the procedures and operatingconditions described herein can be varied considerably Without departingfrom the basic principles of this invention.

We claim:

1. The method of treating soybean oil to improve its quality and torecover a xanthophyll concentrate as a by-product, comprising extractingcrude degummed soybean oil containing xanthophyll With methanol at atemperature above 40 F. up to about 140 F., the extraction systemincluding said methanol and said soybean oil containing less than 1percent water by weight during said extraction, continuing saidextraction until at least a major portion of the xanthophyll has beenextracted into the methanol phase while said methanol phase containsless than 2% by weight of the triglycerides of said soybean. oil,separating the xanthophyll-containing methanol phase from the oil phase,removing the methanol from the extracted material in said methanol phaseto obtain a xanthophyll concentrate, and also removing the methanol fromthe oil phase to obtain a soybean oil product of improved quality.

2. The method of treating soybean oil to improve its quality and torecover a xanthophyll concentrate as a 6 by-product, comprisingextracting xanthophyll-containing soybean oil with methanol at atemperature above 40 F. up to about F., said soybean oil at the start ofsaid extraction being substantially free of gums and containing at least98 percent by Weight of triglycerides and in excess of 0.1 percent ofxanthophyll and other non-triglyceride organic material, the extractionsystem including said methanol and said soybean oil containing less than1 percent Water by weight during said extraction, continuing saidextraction until the oil phase contains less than 0.1 percent of saidnon-triglyceride material and the methanol phase contains less than 2%of the triglycerides of said soybean oil together with the extractedxanthophyll, thereafter separating the said oil phase from the methanolphase containing the xanthophyll and other non-triglyceride material,removing the methanol from the extracted material in said methanol phaseto obtain a xanthophyll concentrate, and also removing the methanol fromthe oil phase to obtain a soybean oil product of improved quality.

3. The method of treating soybean oil, comprising subjecting degummedsoybean oil containing xanthophyll to a multiple stage countercurrentextraction with methanol at a temperature above 40 F. up to about 140F., the extraction system including said methanol and said soybean oilduring said extraction containing less than 1 percent Water by Weight,continuing the extraction until the methanol phase contains anappreciable amount of said xanthophyll together with less than 2% byweight of the triglycerides of said soybean oil, separating thexanthophyll-containing methanol phase from the oil phase, and removingthe methanol from the extracted material in said methanol phase toobtain a xanthophyll concentrate, and also removing the methanol fromthe oil phase to obtain a soybean oil product of improved quality.

4. The method of treating soybean oil to improve its quality and torecover a xanthophyll concentrate as a by-product, comprising subjectingsoybean oil to a multiple stage countercurrent extraction with methanolat a temperature above 40 F. up to about 140 F., said soybean oil at thestart of said extraction being substantially free of gums and containingin excess of 0.1 percent by weight of xanthophyll and othernon-triglyceride organic material including the xanthophyll therein butnot over 1 percent of said non-triglyceride material, the extractionsystem including said methanol and said soybean oil during saidextraction containing less than 1 percent water by Weight, continuingsaid extraction until the oil phase contains less than 0.1 percent ofsaid non-triglyceride material and'the methanol phase contains less than2% by weight of the triglycerides of said soybean oil together with theextracted xanthophyll, separating the xanthophyll andnon-triglyceride-containing methanol phase from the oil phase, removingthe methanol from the extracted material in said methanol phase toobtain a xanthophyll concentrate, and also removing the methanol fromthe oil phase to obtain a soybean oil product of improved quality.

References Cited in the tile of this patent UNITED STATES PATENTS2,357,881 Dombrow Sept. 12, 1944 2,841,495 Stewart July 1, 19582,924,525 Kruse Feb. 9, 1960 OTHER REFERENCES Schertz: Jr. Agri.Research XXX, March 15, 1925, pages 575577.

1. THE METHOD OF TREATING SOYBEAN OIL TO IMPROVE ITS QUALITY AND TORECOVER A XANTHOPHYLL CONCENTRATE AS A BY-PRODUCT, COMPRISING EXTRACTINGCRUDE DEGUMMED SOYBEAN OIL CONTAINING XANTHOPHYLL WITH METHANOL AT ATEMPERATURE ABOVE 40*F, UP TO ABOUT 140*F., THE EXTRACTION SYSTEMINCLUDING SAID METHANOL AND SAID SOYBEAN OIL CONTAINING LESS THAN 1PERCENT WATER BY WEIGHT DURING SAID EXTRACTION, CONTINUING SAIDEXTRACTION UNTIL AT LEAST A MAJOR PORTION OF THE XANTHOPHYLL HAS BEENEXTRACTED INTO THE METHANOL PHASE WHILE SAID METHANOL PHASE CONTAINSLESS THAN 2% BY WEIGHT OF THE TRIGLYCERIDES OF SAID SOYBEAN OIL,SEPARATING THE XANTHOPHYLL-CONTAINING METHANOL PHASE FROM THE OIL PHASE,REMOVING THE METHANOL FROM THE EXTRACTED MATERIAL IN SAID METHANOL PHASETO OBTAIN A XANTHOPHYLL CONCENTRATE, AND ALSO REMOVING THE METHANOL FROMTHE OIL PHASE TO OBTAIN A SOYBEAN OIL PRODUCT OF IMPROVED QUANLITY.